Scheduled Maturity Dates for Fixed Maturity Securities by Number of Years Until Maturity (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value
Total	$ 3,093,156
Amortized Cost
Amortized Cost	3,135,647
Fixed Maturities
Fair Value
Due in One Year or Less	183,390
Due after One Year Through Five Years	793,254
Due After Five Years Through Ten Years	370,056
Due After Ten Years	542,116
Mortgage-Backed and Asset-Backed Securities	1,194,107
Total	3,082,923	$ 3,057,054
Amortized Cost
Due in One Year or Less	184,761
Due after One Year Through Five Years	801,841
Due After Five Years Through Ten Years	368,933
Due After Ten Years	554,592
Mortgage-Backed and Asset-Backed Securities	1,215,286
Amortized Cost	$ 3,125,413	$ 3,027,408